Example : Devilish schemes.
The cold calculation and diabolic art of some statesmen.
The diabolical expression on his face.
A mephistophelian glint in his eye.

Synonyms : diabolic, diabolical, mephistophelean, mephistophelian

Example : A roguish grin.

Synonyms : rascally, roguish

Example : The socialists are further handicapped if they believe that capitalists are not only wicked but also devilishly clever.

Synonyms : devilishly